Bromide (Br−) is ubiquitous in natural waters and waters impacted by anthropogenic activities including discharge of treated or untreated wastewaters, the releases from coal-fired power plants and hydraulic fracturing operations, and sea water intrusion. Although Br− in drinking water has no direct public health ramifications, it can lead to formation of regulated disinfection byproducts (DBPs) during water treatment, such as bromate (BrO3−), brominated trihalomethanes (THM) and brominated haloacetic acids (HAA). BrO3− is formed during ozonation, while brominated THMs and HAAs can be formed during chlorination. Brominated DBPs are more cyto- and geno-toxic than their chlorinated analogs. Bromate anions are highly toxic for humans and, according to the World Health Organization (WHO), 25 μg/L is the maximum concentration permitted in drinking water. The potential health risks of DBPs have raised concerns, and increasingly stringent regulations are imposed for some DBPs under the Disinfectants/Disinfection Byproduct Rule (D/DBPR) of United States Environmental Protection Agency.
Various alternatives have recently been proposed to remove halide anions such as bromide from drinking water, but none of them have proven sufficiently effective for large-scale application. In a previous study, the efficacy of Ag-doped carbon aerogels in removing chloride, bromide, and iodide anions from surface and mineral waters was analyzed. Sánchez-Polo et al., Water Res., 41(5):1031-7 (2007). The results obtained indicated a high adsorption capacity (7.32 μmol halide/g aerogel) for the carbon aerogel. However, the results obtained also showed that the percentage of Ag adsorption sites available to halides anions was very low, indicating that most of the Ag(I) adsorption sites were not accessible for the halide adsorption process, possibly because of the low surface area of the materials used (500 m2/g). Numerous other materials, including metal impregnated sorbents (e.g. zeolite and alumina), activated carbons (ACs), activated carbon fibers, and anion exchange resins have been evaluated for removal of Br− from water. However, there is as yet no well-established technology to control Br− at water treatment plants.
There is also a need for providing purified bromine or bromide, since bromine is useful in many industrial processes. While bromide is an undesirable contaminant in natural waters and waste water, bromide content in aqueous fluids of these types is typically very dilute. Accordingly, there is a need for a process for removing and purifying bromide ions from aqueous sources.